How to create an Interactive 2D map

Hi, I'm creating a virtual tour on a museum and I want a 2D interactive map at the start where the user can choose his starting area. I've got a black and white 2D plan of the museum and I created colored area for each room with an alpha channel for the rest. Is it possible in a GUI to enable an image(the colored area) when the mouse passes over a part of the 2D plan. And then if I click on it, it load the designated room.

 var carte: Texture2D; 
 var carte_orange: Texture2D;
     
     function OnGUI ()
     {
         GUI.Box (Rect (50,60, 600, 340),map);
         if(GUI.Button(Rect(500,360,150,40),""))    
                 {
                 GUI.Box (Rect (50,60, 600, 340),map_colored);
                 }
      }